1. Field of the Invention
This invention relates to a capacity computing apparatus which computes the capacity of a chargeable secondary battery.
2. Description of Related Art
Japanese Patent Application Laid-Open No. 61-29079 (29079/1986) discloses an apparatus for measuring the capacity of a secondary battery. The disclosed apparatus is provided with a secondary battery, a current-detecting resistance connected in series to the secondary battery and a microcomputer connected to the secondary battery and current-detecting resistance to measure the amount of a charge and discharge of the secondary battery. The apparatus is so designed that a voltage generated in the current-detecting resistance is directly read by the microcomputer.
Meantime, since an 8-bit microcomputer becomes the fashion of the present time, approximately 1.OMEGA. resistance is required so as to directly read even a very small voltage generated in the current-detecting resistance. As the resistance is made larger, however, it becomes difficult to obtain a sufficient output voltage from the secondary battery because the drop voltage is increased due to the increased resistance. As such, it is desirable to restrict the voltage drop in the current-detecting resistance as much as possible to supply a sufficient output voltage to a load connected to the secondary battery. However, this requirement for restriction of the voltage drop invites need of improvement of the accuracy of the microcomputer, resulting in high cost in manufacturing the apparatus itself.